Buoyant material



w. H. MOSS BUOYANT MATERIAL April 24, 1945.

Filed Oct 7, 1943 FIG. I

w. H.Mos$

) l nven lor W Attorneys Patented Apr. 24, 1945 BUOYANT MATERIAL William Henry Moss, London, England, assignor to British Celanese Limited, London, England, a company of Great Britain Application October 7, 1943, Serial No. 505,301 In Great Britain August 7, 1942 8 Claims.

It is often desired to provide boats with a reserve of buoyancy so that they will remain afloat in spite of damage to the hull. This reserve of buoyancy is commonly provided in the form of closed tanks filled with air. In the case of craft which are likely to be exposed to gunfire however, such tanks are not satisfactory since they become ineffective if pierced.

I have now found that a suitable material for imparting reserve buoyancy to water-borne craft which are likely to be exposed to gunfire can be provided in the form of a number of closed containers full of air and constructed of a textile fabric or other fibrous sheet material, e. g., paper rendered water-tight and stiffened by a coating of a cellulose ester or ether or other artificial organic water resistant polymer. Such containers can be packed into suitable compartments in the boat or other craft in numbers sufficient to provide the reserve buoyancy required. The containers may be simply and economically made and the amount of polymer needed in their production is less than if they were moulded or formed from sheet material of the polymer.

A suitable material from which to form the containers is a woven cotton fabric having a weight of about 2 ozs. per square yard. This may be coated with a dope comprising cellulose acetate in solution in a volatile solvent or solvent mixture, so that after drying-off the solvent the coated fabric has a weight of about 8 025. per square yard.

Suitable volatile solvents or solvent mixtures include: acetone, dioxane, and mixtures of methanol or ethanol with benzene or with a chlorinated parafiin such as ethylene dichloride or methylene dichloride. The cellulose acetate may be of the ordinary acetone-soluble kind, e. g., having an acetyl value (calculated as acetic acid) of 52 or 53 to 54 or 55%; or a more highly water resistant cellulose acetate, having an acetyl value between 55 and 62%, e. g., 5658 or 59% may be used.

A convenient way of coating the fabric is to draw it through a bath containing the dope. Other methods may be employed, however, for instance the fabric may be coated by spreading, or by spraying methods. dried, for instance, by passage over heated rollers or by means of a current of warm air. The dried fabric may then be cut into blanks from which the containers of the invention are formed. A very suitable form for such containers is that of a closed cylinder some two or three inches in The coated fabric is height and having about the same diameter as height. The ends are preferably dished to give greater strength. The two ends may be oppositely dished, i. e'., both concave or both convex, but it is preferable for one end to, be convex and the other concave so as to facilitate close packing, the convex end of one cylinder fitting into the space provided by the concave end of the next. Long cylinders of several inches in diameter could also be formed havingtransverse partitions at intervals of a few inches, but this is a less satisfactory arrangement since the cells so formed cannot so readily be tested for water tightness as can individual cylinders. Moreover the cellular construction is less simply made and is less strong than individual cylinders with dished ends. Instead of the cylindrical shape, other regular shapes may be adopted. Thus, for example, containers in the shape of tetrahedra,

cubes, or prisms of triangular, rectangulan.

hexagonal or octagonal section, may be formed. b11011 shapes are, however, less strong than the cylindrical. For ease of manufacture, strength and convenience in use, the cylindrical form is to be preferred. 7

The containers of the invention may be assembled to form slabs or blocks of buoyant mamaterial can be formed in a similar way, using several layers of cylinder one upon another. Units built up of cylindrical containers each united to its neighbours are easier to handle and transport than the individual cylindrical containers. made large enough to support the weight of a man or even several men in the water. Instead of forming the material into individual cylinders, cubes or the like, slabs or blocks of cellular material may be built up from the coated fabric, for instance by cementing between two fiat parallel sheets of coated fabric spaced apart, flanged partitioning walls of the same materiai, but this cellular form of construction is subject to the disadvantages referred to above, of which the most important is the virtual impossibility of testing the water-tightness of an interior cell. It is important that each container, or in the case of cellular material, each cell, shouldbe water-tight and capable of withstanding the Such units may with advantage be v lose acetate, suitable cements include solutions in volatile liquids of cellulose acetate or, other esters or ethers of cellulose, or of polyvinyl acetate. The joints may be made at ordinary temperature or at higher temperatures.

As indicated above, the fabric to be coated is preferably a woven fabric of cotton having a 1 weight of about 2 ozs. per yard. Other fabrics which can be provided with an adherent water proof coating of an artificial film-formin polymer canalsobe employed. Useful results for instance have been obtained with a plain woven cotton fabric of weight aboutl oz. per yard. Insteadof cotton other textile materials of cellulose'or regenerated cellulose can be used. Thus, forex'ample fabrics of linen or of regenerated cellulose made by the viscose process, the cuprammonium process why the saponification of cellulose est'ers'can be used, including fabrics composed of or containingyarn made by the complete saponificationo'f"cellulose acetate yarn of high tenacity. Such high tenacity yarn can be obtained by stretching cellulose acetate yarn of ordinary tenacity in the presence of steam or hot water. In this way regenerated cellulose yarns of tenacity in excess of 2 gms. per denier or more can be obtained. These high tenacity yarns produce fabrics which in addition'to being stronger are of greater water resistance'than fabrics made from regenerated cellulose yarns of lower tenacity.

Instead of. cellulose acetate other water resistant artificial'organic film-forming polymers can be employed, e. g., cellulose propionate, cellu-, lose'butyrate, cellulose acetate-propionate, cellulose acetate-butyrate, cellulose acetate-nitrate; cellulose acetate-stearate, ethyl cellulose, benzyl cellulose; ethyl hex yl.cellulose and other esters and ethers of cellulose, especially those containing a relatively high proportion of ester or ether groups. Water resistantpolymerised vinyl compoundscan also be employed .for example, polyvinyl. acetate, polyvinyl. chloride, polymethyl acrylate, polymethyl.methacrylate and coepolye mers oftwo or more of such unsaturated .substances. e employed is, thatofthe, solid polymerisation roducts of, u aiiiene oritsal yl or. 1ogen.de-, vati es. n ludinscwpo mers of .butadiene and its derivatives ,withother unsaturated substances.

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Buoyant material according to the invention is showrif in the accompanying drawing whereinq Figure "1 is ia isectional elevation of 1 one ofthe -niiisi rs rj e fiiiii eei nd i Figure 2 is a sectional elevation on a smaller scale of a block pr budyan inater 'd formed from v a number of 'contaiilergf'such as" that shownin F gured, e ca ed-i ea outer casing.

Referring W l L 11 win ntain'er shown has a cylindricalbody I formed of A. further class.v of polymer. which can.

"be applied by means of a pressing member inserted from the open end of the cylinder, the

end-member 5 being meanwhile supported in a suitably shaped jig. An inwardly dished endmemb'er I is cemented to the body I by the flange 8'." Owing' to this flange being outside the space enclosed. byv the cylindrical-wall and end-members; the pressure necessary to bond the flange Stuthe inner surface of the cylindrical body I can easily be applied, after the end-member 5 has been fixedin position, for, instanceby run ning, a roller-pressing member roundin contact with, the exposed surface. of theflange. 8, while the cylinder is suitably supported, e. g.', bya closeefitting, external cylindrical casing or.ring. The, curvature, of the end-member. 5 is somewhat greater thanthatof. 1 so as to facilitate the packing of thecontainers end. to endwith the, minim m wastaeeof, space. The container is full .ofair.

Referringnow to Figure 2,, theblock of buoyant material shown comprises an outer casing, 9 filled withcontainers of. the construction shown, in Figure 1. The; outer casing 9 is of thesame material as the, containers. The containers. are. arranged in threetiers, ID, and. I 2,. theconcave ends I of the containers I l ofthe. middle tieraccommodatingthe convex ends ofthe containers of the, lower tier IZand the, convergends of thecontainer Il fitting into the space pro.- vided by the concave ends of the containers Ill-of, the upper tier,

This arrangementserves, both to, minimise the f e pace. between containers in the outercasina and to locate the containers, so increasing the, rigidityof the block. The containers of, each tier are packed in the outer casing as closely .as. is possible without substantial distortion. Each ntainer r fer bly em nt dt he her PI r efm ithw ichitisin ontact.

Having described my invention, what. Ldesire to secure by. tters Patent is:

1. Material suitable for imparting, reserve buoyancy to water-borne craft, said material comprising an assemblyof closed cylinders full of. l e h =Y n e avin ne. nd on ex. n e i j r on ve. he on es nd r one nin into the concave end-of another, said cylinders being-formed of -a textile fabric having a coating, of 1 an. artificial {organic water resistant polymer which stiffens the fabric andrendersit iimservi'ous towaiter. V

2. Material suitable for imparting reserve buoyancy to water b'orne craft, said, material comprisinganassembly of, closed cylinders full' of air, each cylinder having, one end; convex and the other concave?"theIconvex'end of onefittin'gl into the concaveend of another, 'saidcylinde'r'sf being formed or a textile fabric having a coating f of an artificial organic water resistantpolymer which stifie'ns'the fabric and renders it m ner vious to', water, the cylinders. being adhesively united one toa n other.

3. Material suitable for imparting, reserve buoyancy to water borne "craft, said material comprising an assembly of closed cylinders of air, each cylinder having one end convex and the other concave, the convex end of one fittin into the concave end of another, said cylinders being formed of a textile fabric having a coating of an artificial organic water resistant polymer which stifiens the fabric and renders it impervious to water, the assembly of cylinders being provided with an outer casing of the coated textile fabric.

4. Material suitable for imparting reserve buoyancy to water-borne craft, said material comprising an assembly of closed cylinders full of air, each cylinder having one end convex and the other concave, the convex end of one fitting into the concave end of another, said cylinders being formed of a textile fabric having a coating of an artificial Organic water resistant polymer which stifiens the fabric and renders it impervious to water, the cylinders being adhesively united one to another and the assembly of cylinders being provided with an outer casing of the coated textile fabric.

5. Material suitable for imparting reserve buoyancy to water-borne craft, said material comprising an assembly of closed cylinders full of air, each cylinder having one end convex and the other concave, the convex end of one fitting into the concave end of another, said cylinders being formed of a cotton fabric having a coating of cellulose acetate which stiffens the fabric and renders it impervious to Water.

6. Material suitable for imparting reserve buoyancy to water-borne craft, said material comprising an assembly of closed cylinders full of air, each cylinder having one end convex and the other concave, the convex end of one fitting into the concave end of another, said cylinders being formed of a cotton fabric having a coating of cellulose acetate which stiffens the fabric and renders it impervious to water, the cylinders being adhesively united one to another.

'7. Material suitable for imparting reserve buoyancy to water-borne craft, said material comprising an assembly of closed cylinders full of air, each cylinder having one end convex and the other concave, the convex end of one fitting into the concave end of another, said cylinders being formed of a cotton fabric having a coating of cellulose acetate which stiifens the fabric and renders it impervious to water, the assembly of cylinders being provided with an outer casing of the coated cotton material.

8. Material suitable for imparting reserve buoyancy to Water-borne craft, said material comprising an assembly of closed cylinders full of air, each cylinder having one end convex and the other concave, the convex end of one fitting into the concave end of another, said cylinders being formed of a cotton fabric having a coating of cellulose acetate which stifiens the fabric and renders it impervious to water, the cylinders being adhesively united one to another and the assembly of cylinders being provided with an outer casing of the coated cotton fabric.

WILLIAM HENRY MOSS. 

